Electromagnet



Oct. l2, 1937; H. E. HoDGsoN ET AL ELECTROMAGNET Original Filed Sept. 22, 1915") Patented Oct. 12, 1937 UNITED STATES PATENT oFFlcE ELECTROMAGNET of Delaware Application September 22, 1930, Serial No. 483,449 Renewed November 28, 1934 9 Claims.

This invention relates to improvements in electromagnets and while not limited thereto is particularly applicable to lifting magnets.

Lifting magnets are usually provided with a magnet frame having concentrically arranged inner and outer pole projections and a coil unit mounted in the space between such projections. The coil unit is usually held in place by a coil shield, which is secured to the inner and outer poles of the magnet frame and serves to hold the coil unit in place and to also prevent entry of foreign matter, and particularly moisture, to the coil unit. Considerable difliculty has been encountered in securing the coil shield to the 15 magnet frame in a manner to prevent loosening thereof, and it has heretofore been proposed to overcome this diiiiculty by welding the coil shield to the inner and outer poles of the magnet frame. However, magnets of this construction have not proven satisfactory. In practice it was found that ing operation excessive strains were set up in the welded joints which often caused breaking thereof or the material adjacent thereto.

The present invention has among its objects to provide an electromagnet of the welded type which will overcome the aforementioned objection.

Another object is to provide an electromagnet having certain of its parts constructed in a manner which tends to reduce conduction of heat away from the welded joints during the welding operation.

Various other objects and advantages of the invention will hereinafter appear.

The accompanying drawing illustrates two embodiments of the invention which will now be described, it being understood that the embodiments illustrated are susceptible of modification without departing from the spirit and scope of the appended claims.

In the drawing,

Figure 1 is a sectional view of one form of lifting magnet embodying the invention;

Fig. 2 is a fragmentary bottom View of the lifting magnet shown in Fig. 1, and

Fig. 3 is a sectional view of a modified form of lifting magnet embodying the invention.

The lifting magnet illustrated in Fig. l is provided with a circular magnet frame I, having a cylindrical center pole 2 and an annular outer pole 3. A coil unit 4 is mounted in the annular space between poles 2 and 3 which comprises a core member 5 bored to receive pole 2, an annular plate 6 fixed to the upper end of said core upon cooling of the magnet parts after the weld- K member, and a plurality of windings 'I mounted upon said core member, each of said windings being formed of strap material and being insulated in the usual manner.

A metal coil shield 8 is provided for holding the coil unit 4 Within the space between poles 2 and 3 and for sealing the same therein. Said coil shield is preferably constructed of chrome nickel or manganese steel and is provided with a center opening for receiving center pole 2 and an outer edge which fits within a counterbore I in the lower end of outer pole 3. The inner edge of coil shield 8 and the lower end of pole 2 are provided with opposed beveled faces forming a V-shaped recess Ii while the outer edge of said coil shield and the lower end of pole projection 3 are provided with opposed beveled faces forming a recess I2. The inner edge of coil shield 8 is secured to pole 2 by a welded connection I3 which is fused into recess II while the outer edge of said coil shield is secured to the outer pole 3 by Welded connection I4 which is fused into the recess I 2. The welded connections I3 and I4 can be applied by various methods, as for example by arc welding.

During the welding operation there is considerable heating of the coil shield 8 and magnet frame I, and in practice it has been found that contraction of these parts upon cooling thereof after the welding operation tends to subject the welded connections I3 and I4 to excessive strains. In order to minimize strains on the welded connections I3 and I4 the lower face of coil shield 8 is provided with a circular recess I5 adjacent the welded connection I3 and a circular recess I6 adjacent the welded connection I4. The recesses I and I6 permit flexing of the coil shield at the portions adjacent the bottom of said recesses to thereby relieve the welded connections from excessive strains. Also it has been found that recesses I5 and I6 act to effect a reduction in the heat conducted away from connections I3 and I4 during the welding operation, to thereby prevent excessive heating of the windings 'I of the coil unit and to also facilitate making of the welds by retention of the heat at the welds.

In the embodiment shown in Fig. 1 the lower face of pole 2 is provided with a circular recess I'I which prevents rapid conduction of heat away from the connection I3 during the welding operation, and as is apparent a similar groove can be provided in the lower face of outer pole 3 to reduce conduction of heat away from connection I4.

Referring now to Fig. 3, the same illustrates a lifting magnet including a magnet frame hav- Yis insulated in the usual manner.

ing a cylindrical center pole 2l and a removable outer pole 22. A plurality of magnet windings 23 are wound directly upon the center pole 2l, each of which is formed from strap material and The coils 23 are surrounded by aring member 2li formed of magnetic material and having its upper end seated Within a recess 25 in the lower facef'of frame 2U. Recess 25 is of such diameter as to provide a channel around the outer face of ring member'fl and said ring member is secured to frame `Z by a welded connection 25 which is fused into said channel.

The coils 23 are held against aXial movement upon centerV pole 2l by a coil shield 2l which is preferably constructed of chrome nickel or manganese steel. Coil shield 2l bears against a shoulder 28'formed on the lower end of centerpole 2l ring member ZlY and is located slightly above the lower edge of said ring member. The inner edge of coil'shield 2l is secured to pole 2l by a welded connection 29 which is fused into a channel formed by shoulder 28, while the'outer edge of said coil shield is secured to ring member 2d by a welded connection 30 which is fused in the corner between the lower face of said coil shield and the lower edge of said ring member. The lower face ofcoil shield 2l is provided with a circular recess 3i adjacent the welded connection 29 to permit iiexing of-said shield at points adjacent said weld, If desired the lower face ofrcoil shield 2 can be. recessed adjacent the welded connection 39 to permit exing thereof at points adjacent such weld, but in practice it has been foundY that where` ring member 2li is relatively thinjas shown in the drawing, this 'is unnecessary. i

The outer'pole 22 is secured Aat points adjaeach provided with the'usual leads 36 which are connected toa terminal unit 3l housed within a recess in the upper face of the magnet frame.V

Also each of the magnet frames l and 2d has its upper face provided with the usual suspension lugs 38, one of which is shown on each of said frames. d

What we claim as new and desire to secure by Letters Patent is: Y

1. In an electromagnet, the combinationwith a'magnet frame having a cylindrical center pole,

a magnet winding'mounted upon said pole, and Y means for enclosing said winding and for holding the same in position upon said pole, said means including an annular'coil shield and a fused connection between the inner edge of saidcoil shield and said pole, said pole and said shield having channels in the faces thereof parallel to and adja cent said fused connection. Y

2. In a lifting magnetin combination, a magnet frame having spaced inner and outer pole projections, an energizing coil mounted upon said inner pole and arranged within the space between said pole projections, a ringmember located between said winding and said outer pole and havingits upper edge welded to said frame, and an annular coil shield for'holding said windingwin position upon said -inner polefsaid'V coil shield having its inner edge welded to said inner pole projection and its outer edge welded to said ring member.

3. In a lifting magnet, in combination, a magnet frame having spaced inner and outer pole projections, an energizing coil arranged within the space between said pole projections and mounted upon said inner pole, aring-member .surrounding said coil and having its upper edge welded to said frame, and an annular coil shield for holding said coil in position upon said Vinner pole, said coil shield having its outer edge welded to said ring member and its inner edge welded to said innerpolerand having a recess in the lower face thereof permitting iiexing thereof at points adjacent said inner pole. Y

4. In an electromagnet,V in combination, a magnetfframe having spaced poles, a winding mountedV in said frame between said poles, a continuous plate between the poles of said frame to shield said winding and to close the space between said poles of said frame, and welded Vconnections between said frame and'said platethe latter being recessed adjacent said welded con- Y nections to provide relatively flexible marginal portions for strain relief of said welded connections. 5. In an electromagnet, the combination wit a magnet frame having concentrically arranged inner and outer poles, an annular winding mount- Ved between said poles, a continuous annular coil shield forming with said frame a complete enclosure for said Winding, and fused connec-V tions between said magnet frame and marginal portionsof said shield, said shield having por-V tions of reduced thickness parallel to andY immediately adjacent said fused connections to provide for strain relief of said fuse'd connections;

6, In an electromagnet, in combination, amagnet frame having concentrically arranged inner1 and outer poles, an annular windingV mounted upon said frame between said poles, an annular plate mounted between said poles and forming with said magnet frame a Vcomplete enclosure Y ,Y for said winding and continuous welded connections between said magnetV frame and the edges of said plate, said plate having connecting Vmeans between-its body andmarginal portions affording strain relief for said welded connections;

7. In a lifting magnet, in combination, a circular magnet VVframe having concentrically arranged inner and outer pole projections, an auf nular winding mounted upon said frame between said pole projections, an annular plate mounted between said pole projections and forming with said frame a complete enclosure for said winding and continuous welded connections between said pole projections and Vthe inner and'outer edges of said plate, said `plate being channeled adjacent its inner and outer edges to facilitate I iiexing thereof'at points adjacent said welded connections.

e. in a lifting magnet, in corriloinauon,` a cir- ,Vcular magnet frame having concentrically arranged inner and outer pole projections on the Aunder side thereof, an annular winding mounted upon said kframe between said pole projections,

an annular plate mounted between said pole proportions of said plate for strain relief of said Welded connections.

9. In a lifting magnet, in combination, a circular magnet frame having concentrically arranged inner and outer pole projections, an annular winding mounted upon said frame between said pole projections, an annular plate mounted between said pole projections and forming with said frame a complete enclosure for said winding and continuous welded connections between said pole projections and the inner and outer edges of said plate, said plate being recessed to provide relatively flexible portions parallel to and immediately adjacent said Welded connections 5 which afford strain relief of said Welded connections.

HOWARD E. HODGSON. HARRY A. SEDGWICK. 

